KN1607 green guide v6.indd - NetComposites

green guide to composites

green guide to compositesan environmental profiling system for

composite materials and products

green guide to composites an environmental profiling system for composite materials and products

BRE

Jane Anderson

Antonia Jansz

Kristian Steele

Paul Thistlethwaite

NetComposites

Gordon Bishop

Adam Black

BRE is committed to providing impartial and authoritative information on all aspects of the built environment for clients, designers, contractors, engineers, manufacturers, occupants, etc. We make every effort to ensure the accuracy and quality of information and guidance when it is first published. However, we can take no responsibility for the subsequent use of this information, nor for any errors or omissions it may contain.

BRE is the UK’s leading centre of expertise on building and construction, and the prevention and control of fire. Contact BRE for information about its services, or for technical advice, at:BRE, Garston, Watford WD25 9XXTel: 01923 664000Fax: 01923 664098Email: [email protected] www.bre.co.uk

Copies of this publication are available from:NetCompositesorwww.brebookshop.comorIHS Rapidoc (BRE Bookshop) Willoughby Road, Bracknell RG12 8DWTel: 01344 404407Fax: 01344 714440Email: [email protected]

Published by BRE BookshopRequests to copy any part of this publication should be made to:BRE Bookshop Building Research Establishment, Watford WD25 9XXTel: 01923 664761Fax: 01923 662477Email: [email protected]

Printed on recycled paper

BR 475© Copyright BRE and NetComposites 2004First published 2004ISBN 1 86081 733 5

BRECentre for Sustainable ConstructionGarston, Watford WD25 9XXTel: +44 (0)1923 664414Fax: +44 (0)1923 664103Web: www.bre.co.uk

NetCompositesTapton Park Innovation CentreBrimington Road, Chesterfield S41 0TZTel: +44 (0)1246 541918Fax: +44 (0)1246 563322Web: www.netcomposites.com

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Acknowledgements

Part 1: Introduction Background 1 Purpose and Scope 1 How to Use this Guide 1 The Web-Based Guide 2

Part 2: How this guide was compiled Life Cycle Assessment 3 Sources of Data 3 Environmental Issues 4 Social Issues 5 The Green Guide Ratings 5

Part 3: Production stages Introduction 7 Material Choice 9

Matrix Materials 9 Fibres 11 Pre-impregnated Materials 13 Core Materials 14

Process Choice 15 Gelcoats 15 Material Preparation 16 Matrix Application 17 Mould Operation and Consolidation 18 Equipment Environmental Impacts 19 Low Impact Process Stages 20

Part 4: Manufacturing processes Introduction 21 Hand Lay-Up 22 Spray-Up 23 Vacuum Bag Moulding 24 Resin Infusion 25 Resin Transfer Moulding 26 Autoclave Moulding 27 Pultrusion 28 Compression Moulding 29

Part 5: Green Guide ratings Introduction 30 Double-Curvature Panel 1m2 31 Flat Sandwich Panel 1m x 8m 33 Complex Moulded Component 35

Glossary 36

contents

This document has been produced as the output from a collaborative project, ‘A simplified guide to assessing environmental, social and economic performance for the composites industry (COMPASS)’, part funded by the UK Department of Trade and Industry through the Sustainable Technologies Initiative. This guide concentrates on environmental and social impacts.

The production and content of this document have been steered by the following organisations, representing a cross-section of the composites industry, and we would like to acknowledge their valuable input and contributions.

Composite Tooling and StructuresCurv Composites Engineered CompositesFibreforce CompositesHexcel Klargester Environmental Lotus EngineeringMenzolit UKMichael Stacey ArchitectsNetwork Group for Composites in Construction (NGCC)Plastech Thermoset TechtronicsPolymer Engineering PolynormReichholdSaint-Gobain VetrotexTaylor WoodrowVestas Blades UK

acknowledgements

1

BackgroundProducts made from composite materials can offer significant environmental benefits because of their characteristically low weight, good mechanical properties and excellent resistance to corrosion. For example, composites used in cars can reduce the overall weight of the car and so offer fuel savings through the lifetime of the vehicle. However, although the in-service environmental benefits of composites are known, there is far less understanding of the environmental and social implications associated with the manufacture of composite materials and products.

Issues affecting the industry include health and safety, the emission of volatile organic compounds (VOCs), energy consumption and toxicity from manufacture. Alternative materials and technologies (such as closed mould processes, natural fibres and low-styrene resins) have been developed to address these problems, but to date there has still been confusion within the industry as to the detailed benefits of these alternatives.

Purpose and Scope This guide has been created to enable the composites sector to understand the environmental and social impacts associated with composite production and assist with the decisions made about material and process choice. The materials and processes modelled are rated from A (good) through to E (poor). Twelve different environmental impacts are individually scored and totalled to give an overall environmental impact summary rating. Two social impact ratings are also given.

When measuring environmental impact it is important to consider all the influences through the life of the product. This process is known as Life Cycle Assessment (LCA) and it has been used in this guide for environmental investigation. Because this guide concentrates on materials and manufacturing, as opposed to in-service performance, the impacts associated with products beyond the factory gate (the use, maintenance and disposal stages of the life cycle) have not been assessed.

Within the system boundaries for the LCA, three typical product types have been chosen to reflect a range of different components commonly manufactured using composites:• A double curvature panel

– this has a surface area of 1m2 with a panel stiffness equivalent to a 4mm thick chopped strand mat laminate.

• A flat sandwich panel – measuring 1m x 8m with a 25mm thick core, having a panel

bending stiffness equivalent to a sandwich panel with a 4mm thick chopped strand mat skin.

• A complex moulded component – with a volume of 770cm3.

Similarly, production processes and materials have been selected to provide a balance between systems that are commonly used across the majority of the composites industry and emerging materials with the potential to provide an environmental benefit. For this reason, materials such as hemp fibre and self-reinforced polypropylene have been included in the guide, but materials that are more specific to a single sector (eg aramid fibre) have not been included.

Within each specific process there are still many processing variations (eg methods for mixing, curing and trimming) in addition to the material choice possibilities. To enable fair comparisons, a base case has been selected for each process. This is used throughout the guide to allow the merits of each process variation to be assessed.

How to Use this GuideThis document is split into five parts:

Part 1 – introduction: The introduction outlines the intent of the guide and gives the overall structure. The life cycle assessment method is introduced along with what has been chosen to be modelled and why.

Part 2 – how this guide was compiled: This section looks in more detail at the life cycle assessment method used in the guide. It outlines which environmental and social factors are being measured and how the ratings are obtained.

Part 3 – production stages: This part of the guide provides background on the social and environmental impacts of the individual stages of production. Guidance then follows on the relative importance of the different production stages, the choices available and the implications of those choices. This part of the guide is designed for situations where a manufacturer is considering just one specific part of the process (eg the mixing stage), as well as to provide greater detail and background information alongside other parts of the guide.

Part 4 – manufacturing processes: This part provides detailed information on the environmental and social impacts of each of the main composite manufacturing processes, showing which stages of each process have the greatest effect. Guidance is also included on process variations that can improve or worsen the environmental impact.

Part 5 – Green Guide ratings: This part contains the A to E Green Guide ratings for a wide range of composite materials and processes, for each of the three product types.

For each product type direct comparisons can be made between different process and material choices.

part 1:introduction

2 introduction green guide to composites

The Web-Based GuideThis paper based guide provides quick and easy guidance to manufacturers of composites to help them minimise the environmental impact of the products they supply. However, it can only provide basic guidance – the parallel web based guide provides more information and allows users to make more specific or detailed comparisons. The web based guide expands on the information provided in this guide enabling users to compare a far broader range of materials and processes, as well as allowing them to focus in detail on the areas of composite production specific to their own needs.

The web-based guide can be found at: www.netcomposites.com/composite-tools.asp

BRE Green GuidesBRE use LCA to provide guidance on the environmental impacts of construction products and processes. They have produced a number of tools and publications as part of this work, one of which is the Green Guide to Specification1, which rates building materials and components on a scale of A to C. This document has been the basis for this new guide on composites.

In common with BRE’s other LCA tools and publications, this Green Guide uses the BRE Environmental Profiles Methodology as its LCA approach. An LCA Methodology is a description of the rules that need to be followed to ensure that the LCA is completed fairly and that the results can be used for comparison. The BRE Environmental Profiles Methodology is compliant with a number of ISO standards (ISO 14040 series2) which have been developed to standardise and define the manner in which life cycle assessments should be undertaken. The reader should also be aware of ISO standard 140203 on Environmental Labels and Declarations.

Further information on the BRE Environmental Profiles Methodology can be found on the BRE website: www.bre.co.uk/envprofiles.

1 The Green Guide to Specification: Third Edition, Jane Anderson, David Shiers and Mike Sinclair, Blackwell Science, Oxford, 2002.

2 BS EN ISO 14040:1997 Environmental Management – Lifecycle Assessment – Principles and Framework.

3 BS EN ISO 14020:2001 Environmental Labels and Declarations – General Principles.

3

Life Cycle Assessment (LCA)The environmental data in this Green Guide to Composites is generated using a technique known as Life Cycle Assessment. LCA is a method of measuring the environmental impacts of a product through its life cycle, often from the cradle to the grave. However, this Green Guide to Composites has studied the life cycle impacts from cradle to factory gate.

In this guide, the LCA has included the impacts associated with the extraction of oil and minerals as precursors to the resin and fibre, the manufacture of the materials, any requirements for transport or packaging and finally the composite manufacturing process itself. It is worth noting that the use of the product, beyond the factory gate, can have a significant effect on the overall environmental impact of the part. However, this guide has been designed only to address the materials and manufacturing processes.

In LCA it is important to ensure fair comparison between different products, and this can only be achieved if the comparison is based on a function that the products are designed to meet. For example, to compare the environmental performance of two products for use as a car bonnet, then each product would first need to meet the bonnet’s functional requirements (eg area, strength and stiffness) for the comparison to be valid.

Within this guide therefore, three generic product types have been defined, each with their own criteria, to allow manufacturers to consider environmental data most suited to their particular product. For each of the three products, the amounts of material required and processes necessary have been calculated on the basis of the given criteria so that the results are product specific, and can be used to make comparisons between the impacts of different materials and processes.

Sources of Data LCA data on the principal raw materials – the polymers, fillers and fibres, have been sourced from internationally recognised databases. Where necessary, this data has been amended or adjusted based on data provided by industrial partners to reflect current UK practice.

For the manufacturing processes, data has been sourced from manufacturers, processors, suppliers or publications. In some instances, it has been necessary to extrapolate data for processes, eg for larger or smaller components, from data provided to the project. In these cases, BRE, NetComposites and the industrial partners have used their best judgement to ensure this gives as accurate a result as possible.

Emissions to air

Emissions to water

Emissions to land

Energy resources

Material resources

Water resources

The composite product system

Inputs Upstream Downstream Outputs

Productionof electricity

Water supply

Production ofby products

Production offuels

Production ofprimary materials

Manufacturing ofcomposite products

Use and service life

Maintenance andreplacement

Wastemanagement

Deposition

End-of-life and Demolition

Figure 1: Stages of a composite product life cycle

part 2:how this guide was compiled

4 how this guide was compiled green guide to composites

Environmental Issues The following environmental issues have been considered within the Green Guide to Composites.

Climate changeGlobal warming is associated with problems of increased climatic disturbance, rising sea levels, desertification and spread in disease. It has been the subject of major international activity, and methods for measuring it have been presented by the Intergovernmental Panel on Climate Change (IPCC). Gases recognised as having a greenhouse or global warming effect include CFCs, HCFCs, HFCs, methane and carbon dioxide. Their relative global warming potential (GWP) is calculated by comparing their global warming effect after 100 years to the simultaneous emission of the same mass of carbon dioxide.

Fossil fuel depletionThis issue reflects the depletion of the limited resource that fossil fuels represent. It is measured in terms of the primary fossil fuel energy needed for each fuel.

Ozone depletionOzone depleting gases cause damage to stratospheric ozone (the ozone layer). There is great uncertainty about the combined effects of different gases in the stratosphere and all chlorinated and brominated compounds that are stable enough to reach the stratosphere can have an effect. CFCs, Halons and HCFCs are the major causes of ozone depletion. Damage to the ozone layer reduces its ability to prevent ultraviolet (UV) light entering the earth’s atmosphere, increasing the amount of harmful UVB light reaching the earth’s surface.

Human toxicity to air† and human toxicity to water†The emission of some substances (such as heavy metals) can have impacts on human health. Assessments of toxicity are based on tolerable concentrations in air, water, air quality guidelines, tolerable daily intake and acceptable daily intake for human toxicity. Impacts to air and water have been combined in the ratings tables shown in Part 5.

Ecotoxicity†

The emission of some substances such as heavy metals can have impacts on the ecosystem. Assessment of environmental toxicity has been based on maximum tolerable concentrations in water for ecosystems.

Waste disposalThis issue reflects the depletion of landfill capacity, the noise, dust and odour from landfill (and other disposal) sites, the gaseous

emissions and leachate pollution from incineration and landfill, the loss of resources from economic use and risk of underground fires etc. Because there is insufficient data available on the fate of materials in landfill or incineration, a proxy figure for these impacts is measured by tonnes of waste produced.

Water extractionThis issue is included because of the value of water as a resource and to reflect the depletion, disruption or pollution of aquifers or disruption or pollution of rivers and their ecosystems due to over extraction.

Acid depositionAcidic gases such as sulphur dioxide (SO2) react with water in the atmosphere to form acid rain. When this rain falls, often a considerable distance from the original source of the gas, it causes ecosystem impairment of varying degrees, depending upon the nature of the landscape ecosystems. Gases that cause acid deposition include hydrogen chloride, hydrogen fluoride, nitrogen oxides and sulphur oxides. Ammonia, a non acidic gas, also plays an important part in the long range transport of the acidic pollutants through the formation of relatively stable particles.

Eutrophication (over-enrichment of water courses)Nitrates and phosphates are essential for life, but increased concentrations in water can encourage excessive growth of algae, reducing the oxygen within the water. This can lead to increasing mortality of aquatic fauna and flora and to loss of species dependent on low-nutrient environments. Emissions of ammonia, nitrates and phosphates to air or water all have an impact on eutrophication.

Summer smog (low level ozone creation)In atmospheres containing nitrogen oxides (a common pollutant) and volatile organic compounds (VOCs), ozone creation occurs in the presence of radiation from the sun. Although ozone in the upper part of the atmosphere is essential to prevent ultraviolet light entering the atmosphere, increased ozone in the lower part of the atmosphere is implicated in impacts as diverse as crop damage and increased incidence of asthma and other respiratory complaints.

Minerals extractionThis issue reflects the total quantity of mineral resource extracted. This applies to all minerals, including metal ore, and applies to both UK and overseas extraction. The extraction of minerals in the UK is a high profile environmental topic but the minerals themselves are not considered to be scarce. Instead, this issue is a proxy for levels of local environmental impact from mineral extraction such as dust and noise. It assumes that all mineral extractions are equally disruptive of the local environment.

†Toxicity: It should be noted that issues relating to toxicity generate much debate. Manufacturers are advised to carefully review the material supplier’s guidance, to note any relevant regulations, codes and standards appropriate to different industries and materials and to consider the context and application within which the materials are to be used. The results in The Green Guide do consider some toxic effects, but these should in no way be considered comprehensive, for any of the material alternatives considered. Many of the chemicals used in society have not undergone a risk assessment and assessment techniques are still often inconsistent.

green guide to composites how this guide was compiled 5

Social IssuesMany of the environmental issues detailed above also infer a social impact. Human toxicity and summer smog are perhaps the most obvious in this respect, as by their very nature they have implications to human health. Additionally, mineral extraction and waste disposal have social consequences and can have detrimental effects on local communities.

Alongside these inferred social influences, this guide also directly considers the effect of the working environment on the employee. Whereas the environmental assessment includes the impacts associated with upstream processes such as oil and mineral extraction, materials production and transport, the social assessment concentrates specifically on the composites conversion processes (hand lay-up, press moulding etc) themselves. In assessing the social impact of composite materials and processes, this guide considers the effect of the working environment on the employee in terms of remuneration and exposure to risk.

Exposure to riskTo evaluate the exposure to risk we evaluated the amount of Personal Protective Equipment (PPE) for each of the different processes included within the study, based on typical best working practice. For each stage of each process the level of PPE required was given a numerical value, based on the risk categories in the table below. It is worth noting that some individual manufacturing environments may well have a very different risk profile to the one shown below. For example in large plants where safety helmets may be mandatory, but where the risk is relatively low. However, because the overall score is a summary of the risks to each part of the body, discrepancies in any one risk category do not significantly influence the overall score. This table should not be used as any sort of substitute for rigorous risk assessments of specific processes or environments.

The total scores for the amount of PPE used in each process were transposed into comparative ranking scales running from A to E.

RemunerationThe level of remuneration associated with each manufacturing processes was also studied, based on a limited survey of typical salary levels across different sectors and processes within one region of the UK. These comparative remuneration rates were also broken down into five scales running from A to E, with an A rating indicating the highest remuneration rates for the employee. Because the survey was restricted to one region of the UK to reduce the likelihood of geographical variations, this meant that it was only possible to obtain a limited amount of data on remuneration.

The Green Guide RatingsWhen undertaking the studies for this guide, data on impacts from the use of raw materials, energy, manufacturing and emissions associated with the product system under investigation were combined to provide an overall impact in each of the 12 environmental and 2 social impact categories identified above. This approach gives a detailed breakdown of the performance of the product system across the common environmental and social categories.

Within each product type, the results for each issue are then compared. For each issue, there will be a range, with the lowest (minimum) and highest (maximum) impact identified. Figure 2 shows the environmental impacts for sixteen variations plotted on the same axis, running from no environmental impact on the left, to high environmental impact on the right.

A to E ratings are then calculated for each composite product type and issue by assessing where the result lies within the range. An A rating is obtained when the result is within the top 20% of the range with the lowest environmental impact, a B rating when it is within the second 20%, and so on.

In order to ensure that only ‘like with like’ comparisons are made, three separate A to E ranges have been created, one for each product type.

Table showing the risk category ratings for Personal Protective Equipment (PPE)

PPE Risk categories

0* 1 2 3 4

Eye protection No protection required Safety glasses Safety goggles Face screen and

goggles

Respiratory

protection

No protection required Dust mask Half mask Air Stream

Full face mask

Head protection No protection required Safety Helmet

Hand protection No protection required Work/heat resistant

gloves

Cut resistant gloves

Ear protection No protection required Earplugs <90dB Ear muffs >90dB

Body protection No protection required Disposable suit with

hood*It was assumed that safety shoes and overalls should be worn at all times

6 how this guide was compiled green guide to composites

Range

No environmental impact >>> >>>Low environmental impact High environmental impact

A Rating

B Rating

C Rating

D Rating

E Rating

Scores

Minimum Maximum

Environmental Summary RatingsTo assist with using this information, the individual environmental scores are also combined to a single score of environmental performance called a summary rating.

For the environmental summary rating, the different measurement units of each environmental score (eg tonnes of waste) are normalised by dividing them by the impact of one UK citizen. The impact for each issue can then be expressed as a relative proportion of one person’s impact for one year.

A second step multiplies this dimensionless data by a weighting factor, the range of those scores is then used to allocate a letter rating of A to E depending on where in the final range each score lies.

The weighting factors were determined from an extensive BRE research programme in 1999 which included consultation with representatives from seven different groups including local and central government, materials producers, construction professionals, environmental activists and lobbyists, academics and researchers.

A surprising degree of consensus was found across the groups regarding the relative importance of different environmental issues, from which it was possible to assign a weighting to the different issues and hence derive the summary ratings. The environmental issues and their relative weightings are:

Climate Change 38.0%Fossil Fuel Depletion 12.0%Ozone Depletion 8.2%Human Toxicity to Air 7.0%Waste Disposal 6.1%Water Extraction 5.4%Acid Deposition 5.1%Eutrophication 4.3%Ecotoxicity 4.0%Summer Smog 3.8%Minerals Extraction 3.5%Human Toxicity to Water 2.6%

Figure 2: Green Guide environmental rating scale

7

IntroductionWithin this guide the process of manufacturing a composite product has been split into a number of different stages. This part of the guide is designed to provide information on the environmental and social impacts of each manufacturing stage, as well as the choices that exist within them.

Figure 3 shows the stages of composite product manufacture within the framework of life cycle assessment. Energy, material and water resources are used in creating the product, whilst the associated process has resultant emissions to air, land and water.

Each stage of the manufacturing process has an environmental impact that contributes to the total impact for that composite product, and there may be a number of choices for each manufacturing stage.

These impacts of each manufacturing stage vary in their magnitude and range, and to select the best environmental option it is necessary to see which parts of the process contribute the most to the overall total.

Material Choice

Matrix Fibre

Mould preparation

Preparation of materials

Application of materials

Mould operations and consolidation

Curing and post curing

Trimming the component

Cleaning and disposal of equipment

Emissions to air

Emissions to land

Emissions to water

Energy resources

Materials resources

Water resources

Figure 3: Generic illustration of composite product manufacture

part 3:production stages

8 production stages green guide to composites

The bar chart in Figure 4 shows the range of possible impacts within each manufacturing stage, for all the possible material and process options evaluated. The impacts for a single process (the hand lay-up base case) are shown as black dots and the relative impact of each stage for this product is shown in the pie chart.

In Figure 4 the bars refer to the range of possible values of environmental performance. The lower boundary of each range is the lowest possible impact where this stage of composite manufacture is applied and if the stage is not applied (eg where no gelcoat is used) then the impact for that stage is zero.

Figure 4 shows that the embodied impacts of the materials have the largest environmental impact. However, depending on the composite process, many of the other stages can contribute a sizeable proportion of the total environmental impact. Not all of the choices within process stages are mutually exclusive and the choice of one may affect the magnitude and range of impacts of another.

This co-dependency is most evident within the choice of process, fibre and matrix. For instance, if a fibre of low environmental impact

is chosen, it may not then be possible to choose the matrix with the lowest environmental impact. These choices also determine the amount of material needed for manufacture, where material quantity has a significant influence on the overall impact.

In this guide we have studied a selection of matrices, fibres and pre-impregnated fibre combinations. These materials have an inherent embodied environmental impact that arises from the extraction of raw materials and the refining of those materials into products such as matrices and fibres. The upstream embodied environmental impacts are discussed in the material choice subsections that follow.

In addition to the embodied environmental impact of these materials, there are also further process related impacts arising from their use in the factory. These impacts are discussed in the process choice subsections that follow. Beyond the factory gate, the impacts associated with composite product manufacture become a part of the embodied impact of the finished composite product.

Guidance now follows on each stage individually, where issues of co-dependency are reviewed where applicable.

Equipment clean/disposalMould cleaning

Post productionTrimming

CuringConsolidation

Core (embodied)Matrix (application)Matrix (preparation)

Matrix (embodied)Fabric (embodied)

Gelcoat (application)Gelcoat (embodied)

Mould release agent

Low HighNormal release agent (<1%)

Gelcoat (6%)

Gelcoat application (brushed) (2%)

Chopped strand mat (CSM) (7%)

Polyester (66%)

Open mixing polyester (8%)

Brushing polyester (8%)

Consolidate by roller (2%)

Cure at room temperature (0%)

Trim by electric hand (<1%)

Acetone mould cleaning (1%)

Figure 4: The magnitude and range of environmental impacts for stages of composite product manufacture (bar chart). The pie chart opposite shows the relative impact of each process in the hand lay-up base case (also shown as dots on the bar chart)

green guide to composites production stages 9

Material Choice: Matrix Materials

The matrix is made up of a polymer and often other components such as catalyst, accelerator and filler. The polymers are based on fossil fuels, and have considerable environmental impact associated with their raw materials extraction, processing and manufacture. Due to the high proportion of the matrix and its inherent environmental properties, in most cases it will be the greatest cause of environmental impact for the composite product. A description of the matrix materials studied is given below.

Base PolymersFrom the range of polymers used in composite products, this study has focused on three main types:• Polyester resins • Epoxy resin • Polypropylene

Catalysts and AcceleratorsVarious catalysts and accelerators are used within composite manufacture, such as MEKP and cobalt napthenate. Although these are used in very small quantities and hence do not directly affect the environmental impact of the resin, their use does affect cure time and temperature and, where they can reduce the use of ovens or autoclaves, they can bring a beneficial environmental contribution.

FillersFillers are normally mineral based with much smaller processing and manufacturing impacts than the base polymers. Because the filler replaces some of the polymer within the matrix, there can be considerable environmental advantage to their use. Two fillers have been modelled in this study:

Alumina Trihydrate (ATH) ATH is an intermediary product of the production of aluminium from bauxite and is used as a fire retardant additive. The environmental impacts are associated with mineral extraction and processing energy.

Calcium Carbonate (CaCO3) Calcium carbonate is usually used to reduce the amount of resin used whilst offering a small increase in stiffness. Environmental impacts associated with calcium carbonate production are primarily related to mineral consumption.

Embodied Environmental Impacts Figure 5 indicates clearly that the matrix usually has the greatest individual impact in the composite process. The polyester in the hand lay-up base case represents 65% of the final impact and is the matrix with the greatest environmental impact of all those modelled in the guide. This impact can however be reduced by choosing alternative matrices.

Figure 5: Pie and bar chart showing the relative impact and range of impacts of the matrix, the dot and pie chart representing the impact of matrix in the hand lay-up base case



CuringConsolidation




Mould release agent

Low High


For direct comparison, the environmental impact of each matrix by weight is shown in Figure 6. Because different quantities of each of the different matrices are required to make a component with the same structural performance, a second bar chart is shown alongside which compares the embodied environmental impact of the matrix and fibre required to make the 1m2 double curvature panel. All the matrix/fibre embodied impact bar charts in this section (Figures 6, 8, 9 and 10) are on the same scale to allow direct comparisons between the results in each chart.

From Figure 6 it can be seen that, by weight, polypropylene has the lowest environmental impact with unfilled polyester having the highest. Epoxy resin has a lower impact than polyester, but using calcium carbonate filler halves the impact of polyester simply by reducing the amount of resin used.

Low styrene polyesters are not shown on this graph because they have comparable embodied impacts to normal polyesters. They do however offer an environmental benefit in the mixing and application stages discussed later.

In the matrix/fibre embodied impact assessment, the fibre – modelled as a random glass mat – has been kept constant and different resin types have been investigated. For GMT, the impact of the GMT compounding process is included as it is part of its embodied impact and ensures the comparison is fair. The results show a similar trend to that seen in the comparison of matrix materials by weight.

Recommendation: When using polyester, the inclusion of fillers greatly reduces the environmental impact, with calcium carbonate having a lower environmental impact than ATH. Polypropylene has a lower impact on the environment than the epoxy and polyester resins.

Figure 6: The relative impact of matrices by weight alongside the relative** embodied impacts of the matrices and fibres needed to make the 1m2 double curvature panel ** relative to all matrix/fibre combinations in Figures 6, 8, 9 and 10.

Matrix Relative impact by weight Fibre Volume fraction

Matrix/fibre embodied impact

Polyester CSM 20%

Polyester +50% ATH CSM 20%

Polyester + 50% CaCO3 CSM 20%

Epoxy resin CSM 17%

Polypropylene CSM* (GMT) 13.5%

0 20 40 % 60 80 100 0 20 40 % 60 80 100

* CSM – Chopped glass strands

Fibre

Matrix

Material compounding


Material Choice: Fibres

This guide has reviewed four reinforcement fibres, including glass, carbon, hemp and polypropylene.

Glass Glass is used in a number of different forms, including rovings, woven fabrics, chopped strand mat and chopped fibres. Environmental differences occur mainly due to the differing energy requirements between the methods of producing the different fibre forms.

CarbonCarbon fibre has a relatively high environmental impact, closely linked to energy demand during its manufacture. However, for the same structural performance less carbon fibre is needed in a composite product when compared with other fibre types, so its comparative environmental impact is reduced.

HempHemp fibre is a natural reinforcement manufactured from an agricultural crop. Whilst there are some impacts that arise from its cultivation, the energy demand is very low which results in a relatively low environmental impact.

PolypropyleneThe constituent materials are a particularly significant part of the environmental impact of polypropylene, and polypropylene fibres have a higher environmental impact than glass and hemp. Whilst a combination of polypropylene fibres in a polypropylene matrix can result in a fully recyclable composite, this has not been assessed in this guide.

Embodied Environmental Impacts Figure 7 shows the range of impacts of the fibre, as well as the position of the impact of the glass fibres in the hand lay-up base case. It can be seen that the impact of the glass CSM is only 7% of the total, but that other fibres and fabric forms can have a greater impact. From Figure 8 it can be seen that, by weight, hemp performs better than glass CSM, woven glass, glass rovings and woven polypropylene. Woven carbon has the highest impact by far.

In the matrix/fibre embodied impacts comparison, each fibre is combined with polyester resin. Although hemp performs best by weight, woven glass actually performs better in a panel with equivalent properties as it requires less material. Woven carbon, having even higher structural qualities, requires the least amount of matrix but still has the highest impact.

The choice of process, and hence volume fraction, can also have an impact on the final assessment, and Figure 9 shows identical materials being used in hand lay-up and RTM processes. The inherent nature of the RTM process means that a higher fibre volume fraction is possible, resulting in lower resin usage and better environmental performance when compared to hand lay-up.

Recommendation: Significant differences exist between the carbon, glass, polypropylene and hemp fibres. Be aware however that it is often the amount of matrix that is combined with the fibre that determines the final impact. Carbon has an inherently high environmental impact, though this is often offset by its superior mechanical properties.

Figure 7: Pie and bar chart showing the relative impact and range of impacts of fibres, the dot and pie chart representing the impact of the fibre in the hand lay-up base case



CuringConsolidation




Mould release agent

Low High


Figure 9: The final embodied impacts of materials used for hand lay-up and RTM processes using identical materials

Figure 8: The relative impact of fibres by weight alongside the relative embodied impacts of the matrices and fibres needed to make the 1m2 double curvature panel

Fibre Matrix Volume fraction (process) Matrix/fibre embodied impact

Hemp Polyester 30% (eg hand lay-up)

Hemp Polyester 45% (eg RTM)

0 20 40 % 60 80 100

Fibre Relative impact by weight Matrix Volume

fraction

(Fibre)

Matrix/fibre embodied impact

CSM Polyester 20%

Woven glass Polyester 32%

Glass rovings Polyester 20%

Hemp Polyester 30%

Polypropylene

Woven carbon Polyester 45%

0 20 40 % 60 80 100 0 20 40 % 60 80 100


The results in Figure 10 can be directly compared with previous charts, showing that glass/polypropylene pre-impregnated materials have the lowest environmental impacts of all the resin and fibre combinations. The polyester based pre-impregnated materials have some of the highest embodied impacts, although the overall process impacts can be very low due to the processes that utilise these materials. The carbon/epoxy prepreg has the highest embodied environmental impact for the 1m2 double curvature panel, although this embodied environmental impact reduces in comparison to other combinations of matrix and fibre in applications where the relatively high strength of the carbon can be fully utilised.

Recommendation: In general, pre-impregnated materials and associated processes offer good environmental performance over more traditional composite materials and manufacturing processes.

For many composites manufacturing processes the fibre and matrix are already combined into a pre-impregnated material. These materials can offer environmental impact reductions as well as providing a cleaner and safer working environment, and several pre-impregnated materials have been included in this guide: • Co-mingled glass and polypropylene fibres (Twintex)• LFT – Long fibre thermoplastic: glass fibre and polypropylene • GMT – Glass mat thermoplastic: glass fibre and polypropylene • PP/PP – polypropylene fibre/tape and polypropylene• SMC – Sheet moulding compound: glass fibre and polyester• Glass/Epoxy Prepreg• Carbon/Epoxy Prepreg

Material Choice: Pre-impregnated Materials

Figure 10: The relative embodied impacts of the pre-impregnated materials needed to make the 1m2 double curvature panel

Pre-impregnated materials Volume fraction Matrix/fibre embodied impact

Co-mingled glass/polypropylene 60%

LFT (Glass/polypropylene) 19%

GMT (Glass/polypropylene) 13.5%

PP/PP 6%

SMC (Glass/polyester) 19%

Glass/epoxy prepreg 55%

Carbon/epoxy prepreg 60%

0 20 40 % 60 80 100

Fibre

Matrix

Material compounding


Material Choice: Core Materials

The most common core materials are low in density, so they can help achieve an increase in panel stiffness for only a very small weight penalty. Investigations have looked at PVC and balsa core alternatives.

The findings of the core study are displayed in Figures 11 and 12. The PVC option is found to have a higher environmental impact than the balsa core by some 60%, due to the inherent differences in the sources of the two materials. Balsa is a wood product with fairly low impacts associated with plantation and milling activity, whilst PVC has quite a high impact arising from the refining processes necessary to extract the material from petroleum sources.

Recommendation: Study findings conclude that environmental saving can be achieved through core choice. The balsa timber core is found to give improved environmental performance compared to a PVC core.



CuringConsolidation




Mould release agent

Low High

Figure 11: Pie and bar chart showing the relative impact and range of impacts of the core (pie chart here is for the 1m x 8m component with a PVC core using hand lay-up base case conditions)

0 20 40 60 80 100

Balsa core

PVC core

%

Figure 12: The relative impacts of different core options


Process Choice: Gelcoats

Gelcoats are often used in composite manufacture to provide a good surface finish to the component. The gelcoat is resin based, often with a filler, and can be applied by brush, roller or spray. From Figure 13 it can be seen that most of the impact is due to the material itself rather than its application.

The impact due to method of application varies due to the difference in emissions given off in each process. Impact variations can be seen in Figure 14 and show that most impact arises from uncontrolled spraying and the least from brushing.

Open mixing of gelcoat formulations can pose a risk to the operator if not handled correctly, or if the correct levels of PPE are not utilised, potentially including respiratory, eye and skin protection. When closed mixing is employed the level of risk may be reduced. The application of gelcoats poses additional risks, such as from spraying and splashing.

Although there have been recent technical developments in the production of low VOC gelcoat systems, due to the developments becoming commercially available after the assessment of materials, these have not been assessed within this guide. Whilst it could be assumed that these systems may have a lower environmental impact, no assessment of these systems has been made.

Recommendation: Minimise impact from emissions by brushing the gelcoat. Uncontrolled spraying increases the impact by a factor of three.

Figure 13: Pie and bar chart showing the relative impact and range of impacts of using gelcoats. Embodied impact of the gelcoat (green) and impact arising from its application (black) are shown on the pie chart for the hand lay-up base case



CuringConsolidation




Mould release agent

Low High

0 20 40 60 80 100

Gelcoat(uncontrolled spray)

Gelcoat(controlled spray)

Gelcoat (rolled)

Gelcoat (brushed)

%

Figure 14: Comparison of environmental impacts of gelcoat application techniques


Process Choice: Material Preparation

This stage in composite product manufacture involves the preparation of both the matrix and fibre, including resin mixing and cutting of the fibres and fabrics.

Resin Preparation Emissions from the styrene used in polyester resins are a significant source of impact during both the mixing and application of a resin. Epoxy and polypropylene do not contain styrene, so there are no significant impacts associated with the mixing of these resins.

Figure 15 shows the impact of open mixing of the polyester resin in the hand lay-up base case and represents 8% of the total impact. Figure 16 shows the comparative impacts of the open mixing of four polyester resins alongside that of closed mixing. The chart shows that the evaporation of styrene during resin preparation can most effectively be avoided through the use of closed mixing, although the use of low styrene polyester resins can reduce the emissions by 50%. The use of filler also provides a reduction in emissions.

Open mixing of resin systems can pose a risk to the operator if not handled correctly, or if the correct levels of PPE are not utilised, potentially including respiratory, eye and skin protection. When closed mixing is employed the level of risk may be reduced.

Recommendation: Resin preparation has a notable contribution to overall environmental impact, and significant environmental improvement can be achieved through closed mixing. If this is not feasible then a low styrene resin or a resin containing a filler will give lower emissions from mixing.

Fibre/Pre-impregnated Material PreparationThe main options available for the preparation of fibres and pre-impregnated materials are either to cut by hand or by machine. The

machine that has been modelled minimises waste by nesting the cut shapes, and it was assumed that this gave a 20% reduction in the quantity of waste material. For materials with a large environmental impact, such as carbon/epoxy, savings can be made by using machine cutting. For materials of low environmental impact, such as hemp, the waste savings made by machine cutting are offset by the power usage of the machine, so there is no overall reduction in environmental impact. However, the effect of fibre preparation on the overall product environmental impact was found to be less than 1% for all the materials studied.

The preparation and application of pre-impregnated materials does not generally carry a significant level of risk to personnel, although there is some risk due to temperature in handling hot thermoplastic compounds and due to cutting and handling prepreg and SMC materials.

0 20 40 60 80 100

Open mixingof polyester

Open mixing ofpolyester + 50% filler

Open mixing of lowstyrene polyester

Open mixing of lowstyrene polyester

+ 50% filler

Closed mixing

%

Figure 16: Comparison of open and closed resin mixing of polyester resins

Figure 15: Pie and bar chart showing the relative impact and range of impacts of matrix preparation. The pie chart and dot represent the impact of polyester preparation in the hand lay-up base case



CuringConsolidation




Mould release agent

Low High


Recommendation: To minimise the environmental impact of material application, closed mould techniques or methods such as autoclave or compression moulding should be used. If an open mould technique or pultrusion is being utilised, then minimizing the styrene content of the resin will reduce the environmental impact. This can be done by using epoxy or a low styrene or filled polyester system, where suitable. With spray-up, using a controlled spray rather than an uncontrolled spray will have a considerable environmental advantage.

Process Choice: Matrix Application

The application of the matrix can have a large environmental impact, mainly due to associated styrene emissions. Impact potential is therefore directly linked to both resin type and application process.

The impacts from applying an unfilled polyester matrix, using a range of methods, are presented in Figure 18. Applying with an uncontrolled spray has the greatest impact, but this can be reduced with controlled spraying. The brushing technique used in hand lay-up and vacuum bagging produces fewer emissions but also includes impacts from the use of acetone for cleaning the brushes. The overall impact however is lower than both of the spraying techniques. The pultrusion method involves larger emissions than brushing due to the large surface area of the resin bath, but again less than for the spraying techniques. Whilst resin injection pultrusion systems may have a lower environmental impact, no assessment of this form of pultrusion has been made.

Closed moulding techniques such as RTM and resin infusion do not create emissions but do incur an energy impact from the injecting and infusing of the matrix. Autoclave and compression moulding use pre-impregnated materials and so have no resin application impact.

The choice of resin also affects the impact of this process stage and Figure 19 shows the variation in impact from brushing different matrices. The same trends can be observed as with resin preparation, with the use of a low styrene resin and using fillers reducing impact considerably. Even though there are no significant impacts in terms of emissions from epoxy resin, there are still impacts from cleaning of the brushes and these impacts occur regardless of which resin is used.

When applying resins by brushing or spraying there are a number of risks to the operator that can be minimised through the use of PPE, such as masks, goggles, disposable suits and gloves. In closed moulding processes, the risk to personnel is greatly reduced.

Figure 17: Pie and bar chart showing the relative impact and range of impacts of resin application. The pie chart and dot represent the impact of application by brush in the hand lay-up base case



CuringConsolidation




Mould release agent

Low High

0 20 40 % 60 80 100

Pultrusion

Uncontrolled spray

Controlled spray

Brushing

Closed moulding

Figure 18: Comparison of impacts from applying polyester resin using a variety of techniques

Figure 19: Comparison of impacts from applying different resins by brush

0 20 40 % 60 80 100

Closed moulding

Brushing epoxy

Brushing low styrenepolyester + 50% filler

Brushing low styrenepolyester resin

Brushing polyester+ 50% filler

Brushing polyester


In the hand lay-up base case example there is an impact due to the acetone needed to clean the roller. In vacuum bagging, the consolidation process impact is purely the power used to create the vacuum, although in RTM and press moulding the consolidation impact is significant and can contribute around 10% of the total impact.

Recommendation: The method of consolidation and its environmental impact is determined solely by the choice of process so it is difficult to achieve improvement. The impacts however can be significant and so potentially could influence process choice.

Figure 21: The relative impacts of the consolidation stage

0 20 40 % 60 80 100

Vacuum bagconsolidation

Consolidationby roller

Consolidation bypress moulding

RTM mould operations

Process Choice: Mould Operation and Consolidation



CuringConsolidation




Mould release agent

Low High

Figure 20: Pie and bar chart showing the relative impact and range of impacts of mould operation and consolidation. The pie chart and dot represent the impact of consolidation by roller in the hand lay-up base case


This section details the impacts from the equipment used in composite manufacture. The embodied impacts that arise from capital equipment such as moulds, RTM equipment, compression presses and pultruders have been ignored as is the norm in LCA studies. This can also be done on the basis that their embodied impact is small given their long life.

Process Choice: Equipment Environmental Impacts



CuringConsolidation




Mould release agent

Low High

The only elements of equipment that have a large environmental impact are the consumables used in the vacuum bagging which are disposed of after each moulding. The impact of the materials and disposal of the vacuum bag is 10% of the basic vacuum bagging process. A significant but much smaller impact results from the use and disposal of the pipes used in resin infusion moulding, contributing 2% of the total basic resin infusion process impact.

Figure 22: Pie and bar chart showing the relative impact and range of impacts of equipment use. The pie chart and dot represent the impact of the use of a vacuum bag in the vacuum bagging base case


TrimmingThe overall influence of trimming on the environmental impact of a composite component is minimal, so no recommendation is given. Manual trimming systems may pose more risk to the operator than automated systems, through exposure to dust and cutting tools.

CleaningAcetone and a butanone/toluene based cleaning agent were studied and both were found to have impacts of less than 2%. In the case of RTM system cleaning, where acetone is used to clean away the residual polyester resin, the cleaning of the machine contributes less than 1% of total basic RTM process impact.

The same finding applied to cleaning of pultrusion equipment with acetone and glycol ether, where again the impact was less than 1% of the total basic pultrusion process. Hence, the recommendation is to choose the type and amount of cleaning agent on the basis of performance in terms of minimising scrap components and increasing mould longevity, as this is likely to have more environmental impact than the embodied impact of the cleaning agent.

Where acetone is regularly used for cleaning moulds and ancillary equipment it is advisable that an acetone recycling unit is used to give both environmental and economic benefits. Throughout this guide we have assumed that, after evaporation during the cleaning process, recycling is used to recover 75% of the remaining contaminated acetone.

Some mould cleaning systems pose a small level of risk to personnel, which can be controlled through the use of PPE such as goggles, gloves and respiratory protection.

Low Impact Process Stages

From Figure 23 it can be seen that the remaining stages of the manufacturing process have very little impact. For these stages only brief recommendations will be given:

Mould PreparationA conventional release agent and an eco-release agent were studied and, for both, the embodied impact of the release agent was found to contribute less than 1% to the overall impact of the process. The recommendation for mould preparation is therefore to choose the type and amount of release agent on the basis of performance in terms of minimising scrap components, as this will have a greater environmental impact than the embodied impact of the mould release itself.

Some mould preparation systems pose a small level of risk to personnel, which can be controlled through the use of PPE such as goggles, gloves and respiratory protection.

Curing and Post CuringCuring in ovens, autoclaves, heated moulds and heated dies were all modelled and in all cases apart from one, the impact was found to be less than 1% of the overall impact. Within the materials studied, the exception to this is SMC compression moulding, where heated moulds cause a large energy impact. Although they have not been studied, this may also be true of other polyester moulding compounds such as DMC or BMC. Additionally, if inefficient ovens, autoclaves or mould heating techniques are used, or if they are not fully loaded, the environmental impacts from curing and post curing can become significant. There may be some risk to the operator from the emission of VOCs during the curing process, which can be controlled through the use of respiratory protection if necessary.



CuringConsolidation




Mould release agent

Low High

Figure 23: The relative impact and range of impacts for the remaining stages of composite product manufacture

21

IntroductionThis part of the guide summarises and prioritises the key environmental issues facing each of the eight common manufacturing processes reviewed by the guide. Whilst it is recognised that the choice of manufacturing process will primarily be influenced by economic and design factors, this guide only considers environmental and social impacts.

The following processes have been assessed within the guide. • Hand Lay-Up• Spray-up• Vacuum Bag Moulding• Resin Infusion• Resin Transfer Moulding• Autoclave Moulding• Pultrusion • Compression Moulding

For each process a base case has been chosen, defined as the most common way of performing that process with the most common materials. This provides a benchmark against which changes in material or process technique can be measured.

Trends and recommendations from Part 3 are summarised for each process, with process variations being highlighted as significant if they change the overall impact of the process by more than 1%. Variations are given for the 1m2 double curvature panel except where the trends are different for the other components.

Details of each base case are included in the assessment of each process, together with a pie chart to show the relative environmental importance of the materials and production stages.

It is important to note that the pie charts illustrate the relative importance of each choice in the base case, and that different choices (eg a different resin) will change their relative impact.

part 4:manufacturing processes

22 manufacturing processes green guide to composites

Hand Lay-UpIn hand lay-up, fibres are impregnated with resin by hand using brushes and rollers. The resultant composite is cured at atmospheric pressure, either at room temperature or in an oven. This process can be used to make the 1m2 double curvature panel and the 1m x 8m sandwich panel case studies.

Figure 24 shows that the largest environmental impact from the hand lay-up process arises from the resin. The majority of this derives from the embodied up-stream impacts of the raw material, followed by the impacts from emissions during the mixing and application of the resin. The embodied up-stream impacts of the fibre and gelcoat are also significant.

All of the options listed in the table below were evaluated and it was found that variations in curing, cleaning and trimming operations had no significant effect on the total environmental impact.

The largest improvement in environmental performance can be achieved through changing the resin and fibre, using a closed technique to mix polyester resins and applying the gelcoat by brush. Compared to unfilled polyester, epoxy gives an improvement of 30%, low styrene polyester an improvement of 7% and 50% CaCO3 filled polyester an improvements of 33%. This is due in part to reductions in the embodied impacts and in part to reductions in emissions.

Changing the fibre from CSM to hemp gives an improvement of 12%, whilst changing to woven glass gives an improvement of 18% (when using unfilled polyester). An improvement of 9% can be made if closed mixing is employed and a deterioration of 3% is incurred when the gelcoat is sprayed (uncontrolled) instead of being brushed. An overall improvement of 48% can be made on the base case when using woven glass, 50% CaCO3 filler, low styrene polyester and closed mixing.

Hand Lay-Up

Base case process Other options modelled

Polyester Resin (80% volume

fraction)

Low styrene polyester resin

Epoxy resin

No filler 15%, 30% and 50% ATH filler

15%, 30% and 50% CaCO3 filler

Chopped strand mat (20% volume

fraction)

Woven glass mat

Hemp (with polyester resin)

No core PVC (for 1m x 8m sandwich panel)

Balsa (for 1m x 8m sandwich panel)

Normal mould release Eco mould release

Gelcoat No gelcoat

Gelcoat applied by brush Rolled gelcoat

Sprayed gelcoat (controlled and

uncontrolled)

Open mixing of resin Closed mixing of resin

Fabric cut by hand Mechanically cut fabric

Resin applied by brush

Roller consolidation

Room temperature cure Oven cure

Trimming by electric hand tool Trimming by CNC machine

Trimming by hand

No post cure Oven post cure

Mould cleaned with acetone Mould cleaned with

toluene/butanone cleaning agent

Figure 24: Breakdown of impacts for the basic hand lay-up process for making the 1m2 double curvature component

Normal release agent (<1%)

Gelcoat (6%)


CSM (7%)

Polyester (66%)



Consolidate by roller (2%)


Trim by electric hand tool (<1%)


Fabric cut by hand (<1%)

green guide to composites manufacturing processes 23

Spray-UpThe spray-up process incorporates chopped glass rovings with catalysed resin and sprays the resultant mix onto the mould surface, with further compaction using rollers if required. Curing is either at room temperature or in an oven, and this process can be used to make the 1m2 double curvature panel and the 1m x 8m sandwich panel case studies.

As with hand lay-up, the resin is the largest contributor to the total environmental impact of the composite. In spray-up, closed mixing of the resin ensures that there are no emissions at this stage, but the spraying process creates large quantities of airborne styrene and hence the emissions during application are very high.

The overall impact can be reduced by 6% by using a controlled spraying technique, 6% by using a low styrene resin and 31% by using 50% CaCO3 filler. An improvement of 1% can be achieved by controlled spraying of the gelcoat and 3% by brushing.

The impacts from curing, mould cleaning and trimming all have little significance on the overall environmental performance and no marked improvement can be achieved by varying these options.

Figure 25: Breakdown of impacts for the basic spray-up process for making the 1m2 double curvature component

Spray-Up


Polyester Resin (80% volume fraction)

Low styrene polyester resin

No filler 15%, 30% and 50% ATH filler15%, 30% and 50% CaCO3 filler

Chopped Glass Rovings (20% volume fraction)

No core PVC (for 1m x 8m sandwich panel)Balsa (for 1m x 8m sandwich panel)


Gelcoat No gelcoat

Sprayed gelcoat (uncontrolled) Brushed gelcoat Rolled gelcoat Sprayed gelcoat (controlled)

Closed mixing of resin

Fibres chopped in spray gun

Resin applied by uncontrolled spray Resin applied by controlled spray

Roller consolidation


Trimming by electric hand tool Trimming by CNC machineTrimming by hand


Mould cleaned with acetone Mould cleaned with toluene/butanone cleaning agent


Gelcoat (6%)

Uncontrolled spraying of gelcoat (5%)

Glass rovings (8%)

Polyester (62%)

Closed mixing (<1%)

Uncontrolled spraying of polyester (14%)

Consolidate with roller (2%)



Acetone mould cleaning (<1%)


Vacuum Bag MouldingVacuum bag moulding has been considered both as an extension to hand lay-up for increased consolidation, as well as a route for moulding co-mingled and prepreg materials. In this process a vacuum bag is placed over the uncured laminate and a vacuum drawn with the use of a pump, the laminate being held under vacuum during room temperature or oven cure. This process can be used to make the 1m2 double curvature panel and the 1m x 8m sandwich panel case studies.

When a fibre and wet matrix are used, the impacts for the impregnation stage are the same as for hand lay-up, but the addition of vacuum bag consumables contributes 7% to the overall process. All the trends concerning the resin and fibre choice, preparation and application for vacuum bag moulding are also the same as those for hand lay-up.

The vacuum bagging process is also used to process co-mingled and prepreg materials. Compared to using glass/polyester for the 1m2 double curvature panel, a reduction in environmental impact of 52% is achievable when using co-mingled glass/polypropylene, 33% for glass/epoxy prepreg and 2% for carbon/epoxy prepreg. However for the 1m x 8m sandwich panel the structural qualities of the carbon/epoxy prepreg allow a smaller quantity of material to be used, giving a 56% reduction in impact over glass/polyester (comparable to both the co-mingled glass/polypropylene and glass/epoxy prepreg).

The manufacturing route for the prepreg is also important, as the impact of a solvent-impregnated prepreg is 12% higher than a hot melt prepreg.

Vacuum bag moulding


Polyester Resin (80% volume fraction) Low styrene polyester resinEpoxy resin (hand lay-up and prepreg)Polypropylene (co-mingled)


Chopped strand mat (20% volume fraction)

Woven glass mat (hand lay-up and prepreg)Hemp (with polyester resin)Glass roving (co-mingledCarbon fibre (prepreg)



Gelcoat No gelcoat

Gelcoat applied by brush Rolled gelcoat Sprayed gelcoat (controlled and uncontrolled)



Resin applied by brush

Vacuum bag consolidation





Disposal of vacuum bag consumables

Figure 26: Breakdown of impacts for the basic vacuum bag moulding process for making the 1m2 double curvature component


Gelcoat (6%)


CSM (7%)

Polyester (62%)



Vacuum bag consolidation (<1%)



Vacuum bag: materials and disposal (7%)




Resin InfusionIn resin infusion, a vacuum is used to draw resin through dry fabrics under a vacuum bag. Once the resin has wetted out the fabric, the laminate is cured either at room temperature or in an oven. This process can be used to make the 1m2 double curvature panel and the 1m x 8m sandwich panel case studies.

The largest impacts arise from the matrix, fibre and gelcoat, but the vacuum bag and infusion pipes also have a significant contribution. The process can be improved by using closed mixing of the resin (8% improvement), low styrene polyester (4% improvement) or epoxy resin (22% improvement).

Changing the fibre from woven glass to hemp increases the environmental impact by 6% for the 1m2 double curvature panel.

However for the 1m x 8m sandwich panel, where the structural qualities of the woven glass are better utilised, changing to the hemp has an increased impact of 37% due to the higher quantities of materials needed. An increase in environmental impact of 3% is incurred when the gelcoat is sprayed (uncontrolled) instead of being brushed.

Resin Infusion



Low styrene polyester resinEpoxy resin


Woven glass mat (32% volume fraction)

Hemp (with polyester resin)



Gelcoat No gelcoat




Resin applied by vacuum infusion


Room temperature cure Oven cureCure in a heated mould




Disposal of the vacuum bag materials and resin infusion pipes

Figure 27: Breakdown of impacts for the basic resin infusion process for making the 1m2 double curvature component


Gelcoat (7%)


Woven glass (16%)

Polyester (57%)



Resin infusion and consolidation (<1%)




Disposal of RI pipes (2%)



Resin Transfer MouldingIn resin transfer moulding, pressure and vacuum is used to force resin through dry fabrics in a matched mould. Once fully wetted the laminate is cured either at room temperature or in an oven. This process can be used to make the 1m2 double curvature panel, the 1m x 8m sandwich panel and the complex component case studies, and it has been assumed that the higher pressure in resin transfer moulding will allow a higher fibre volume fraction than resin infusion.

Large environmental impacts arise from both the resin and the fibre, so large environmental improvements can be found by changing both of these materials. As before, improvements can be made by using filled polyesters (21% improvement for 50% CaCO3 for the 1m2 double curvature panel).

Changing from woven glass to hemp shows an improvement of 13% for the 1m2 double curvature panel, 2% for the 1m x 8m sandwich panel and 22% for the complex component, whilst changing to carbon increases the environmental impact by 35% for the 1m2 component and 91% for the complex component. However, where the structural qualities of carbon are better utilised, as in the 1m x 8m component, changing to carbon from woven glass decreases the environmental impact by 20%.

The only other variable that has a significant impact is the method of gelcoat application. Uncontrolled spraying of the gelcoat raises the overall environmental impact by 3% compared with applying the gelcoat by brush.

Resin Transfer Moulding



Low styrene polyester resinEpoxy resin


Woven glass mat (45% volume fraction)

Hemp (with polyester resin)Carbon



Gelcoat No gelcoat


Closed mixing of resin


Resin injected under pressure

In-mould consolidation

Cure in a heated mould Room temperature cure




RTM equipment cleaned with acetone flush


Gelcoat (9%)

Gelcoat (brushed) (2%)

Woven glass fabric cut by hand (25%)

Polyester (52%)


Closed mixing (<1%)

RTM inject/infuse resin (2%)

RTM mould operations (8%)

VI or RTM mould heating (1%)



Clean resin infusion system (1%)

Figure 28: Breakdown of impacts for the resin transfer moulding base process for making the 1m2 double curvature component


Autoclave MouldingPrepreg materials are commonly autoclave cured, a process in which the prepreg is consolidated at temperature under pressure and vacuum. This process can be used to make the 1m2 double curvature panel, the 1m x 8m sandwich panel and the complex component case studies.

The environmental impacts for autoclave moulding arise from the prepreg and vacuum bag materials. The material choice is the only option that can significantly affect the total environmental impact with the carbon/epoxy prepreg having a large increase in impact (54% for the 1m2 panel and 114% for the complex component compared to a glass/epoxy prepreg).

By contrast, using a carbon/epoxy prepreg for the 1m x 8m sandwich panel, achieves a reduction in environmental impact of 7%.

With consideration to the manufacturing method of a prepreg, a solution impregnation technique increases the impact of the base case process by 13% compared to a hot melt method. No other variables were found to significantly affect environmental performance.

Autoclave moulding


Glass/epoxy prepreg (45% fibre volume fraction) (hot melt)

Carbon/epoxy prepreg (40% fibre volume fraction)Solution impregnation

No core PVC (for 1m x 8m sandwich panel) Balsa (for 1m x 8m sandwich panel)

Prepreg cut by hand Mechanically cut prepreg


Autoclave cure

Trimming by electric hand tool Trimming by CNC machine Trimming by hand



Disposal of vacuum bag consumables

Prepreg HM (glass epoxy) cut by hand (87%)

Cure in autoclave (<1%)

Vacuum bag consolidation (<1%)




Figure 29: Breakdown of impacts for the autoclave moulding base process for making the 1m2 double curvature component


Pultrusion Pultrusion is a continuous process for making constant cross-section profiles. Fibres and fabrics are continuously pulled through a resin bath and into a heated shaped die in which the resin cures to form the shape of the profile. This process can be used to make the 1m x 8m panel case study, modelled with ribs instead of the core material used in other processes.

The main environmental impacts for pultrusion arise from the resin. The embodied impacts are as discussed in previous sections but the emissions from the resin bath are also large due to the high surface area of the resin bath. Whilst resin injection pultrusion systems may have a lower environmental impact, no assessment of this form of pultrusion has been made within this guide.

Polyesters with 50% CaCO3 filler and 50% ATH filler have been modelled as the matrices used in pultrusion are usually highly filled. The CaCO3 resin performs better than the ATH (as described in Part 3), although the emissions from resin application are the same for both. The only other process option that can be changed, closed mixing, results in an 8% improvement of environmental impact for the process.

Pultrusion



50% CaCO3 filler 50% ATH filler

Woven glass mat and glass rovings (40% volume fraction)


Resin applied by resin bath

Consolidation through die

Cure in heated die

Cut to length by saw

Equipment cleaned

Figure 30: Breakdown of impacts for the pultrusion base process for making the 1m2 double curvature component

Configured glass rovings and woven glass (36%)

Polyester with 50% CaCO3 (59%)

Open mixing polyester +50%CaCO3 (12%)

Pull fibres through resin (14%)

Cure through heated die (<1%)

Saw to length (<1%)

Clean down pultrusion machine (<1%)


Compression MouldingCompression moulding is used for both thermosetting and thermoplastic matrices. Material is placed in the lower cavity of a matched tool, the two halves of the tool are brought together and pressure applied to force the material to fill the cavity. In thermoplastic moulding the material is preheated and placed in a warm mould. By contrast, for thermosetting matrices the material is placed into a hot mould and cured under heat. This process can be used to make the 1m2 double curvature panel and the complex component.

The environmental impacts in compression moulding arise mainly from the materials used. However, considerable impacts can also be attributed to the energy used in the moulding operation, and for SMC the energy used in mould heating. Mould heating for thermoplastics is very low (cool mould) and the pre-heat of the materials occurs in an IR oven which has relatively low energy requirements. An impact specific to PP/PP is the large wastage which can occur due to the quantity of excess material needed to secure it within the mould.

Large improvements can be achieved through material choice. All of the thermoplastic materials show an improvement over the SMC. Eg, by changing from the base case SMC to PP/PP, GMT or LFT, improvements 40%, 37% and 40% respectively are possible.

Compression Moulding


SMC LFT PP/PP GMT

Material cut by hand (SMC) Material cut mechanically (PP/PP, GMT, LFT)

Consolidation by press moulding

No preheat Pre heat in IR oven (PP/PP, GMT)

Cure in heated mould Form in warm mould (PP/PP, GMT, LFT)

Trim by hand (not PP/PP) Trim by CNC machine Trim by electric hand tool (PP/PP)

SMC (84%)

Consolidation by press moulding (11%)

SMC steam heated mould curing (5%)

Trim by hand (<1%)

Figure 31: Breakdown of impacts for the compression moulding base process for making the 1m2 double curvature component

30

IntroductionThis part contains the final Green Guide ratings for complete composite processes. Three sections consider each product type in turn and tabular data is provided for each containing A to E ratings that compare each process.

These tables are intended as a reference for a broad range of composite products. Many of the environmental performance trends already discussed in this guide can be seen within these tables and therefore no further commentary on the results is provided.

The product types were chosen in an attempt to cover the broad range of composite types:• A double curvature panel – this has a surface area of 1m2 with

a panel stiffness equivalent to a 4mm thick chopped strand mat laminate.

• A flat sandwich panel – measuring 8m by 1m with a 25mm thick core, having a panel bending stiffness equivalent to a sandwich panel with a 4mm thick chopped strand mat skin.

• A complex moulded component – with a volume of 770cm3.

When modelling these products, care has been taken to ensure that composites produced within each product type have identical structural and performance characteristics.

Comparisons are only possible within each product type, and it is not possible to compare the ratings between products.

It is possible in this section to compare environmental and social trends for all the main material and process combinations on one page. A to E ratings are shown for each environmental category, along with a summary environmental rating, with an A rating for the lower environmental impacts.

Two A to E social ratings are also given, for risk and remuneration, with an A rating showing a lower level of risk or higher remuneration for the operator.

For each product type the base case processes are listed first in each table, allowing a quick and easy comparison between the main different processes. These rows are followed by sub-sections on each of the main processes relevant to that product, to allow direct detailed comparisons of materials and process options.

It is important to note that this Green Guide rates products on a scale of A to E to provide a more detailed categorisation than the A to C ratings in previous BRE Green Guides. Differences also exist between guides because of variation in product types and study periods. For this reason, comparisons with results in other Green Guides should not be made.

part 5:green guide ratings

green guide to composites green guide ratings 31

Double-Curvature Panel 1m2 A generic component with a surface area of 1m2 and a panel stiffness equivalent to a 4mm thick chopped strand mat laminate. This was selected as being typical of applications as diverse as automotive panels and architectural cladding.

Process Material Choice Environmental Indicators Social

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Hand Lay-Up CSM/Polyester E B C A E C A A D A E B D E

Spray-up Glass rovings/Polyester E B C A E B A B D A D B D E

Vacuum Bag Moulding CSM/Polyester E B C A E C A A D A E B D E

RTM Woven Glass/Polyester C C C A C E A B B A A D C E

Resin Infusion Woven Glass/Polyester D B C A D D A B C A B C C C

Autoclave Moulding Glass/Epoxy Prepreg B C B A A E C B C B A D B B

Compression Moulding SMC C B C A D A A B C A A C B B

Hand Lay-Up CSM/Polyester E B C A E C A A D A E B D E

Woven Glass/Polyester D B B A D C A A C A D C C E

Hemp/Polyester D B B A E A A A C A D A C E

CSM/Polyester +50% CaCO3 filler B A A A C C A A B A D D D E

CSM/Polyester +50% ATH filler C B B A C D A B E A D E D E

CSM/Low styrene (LS) polyester D B C A E C A A D A C B D E

CSM/LS polyester +50% CaCO3 filler B A A A C C A A B A C D D E

CSM/LS polyester +50% ATH filler C B B A C D A B E A C E D E

CSM/Epoxy C C A A B C E C E C A C D E

Hemp/LS polyester +50% CaCO3 filler B A A A C A A A B A D B D E

Spray-up Glass rovings/Polyester E B C A E B A B D A D B D E

Glass rovings/Polyester +50% CaCO3 filler C B B A C B A A B A D D E E

Glass rovings/Polyester +50% ATH filler C B B A C D A B E A D E D E

Glass rovings/Low styrene (LS) polyester D B C A E B A B D A C B D E

Glass rovings/LS polyester +50% CaCO3filler B B B A C B A A B A C D E E

Glass rovings/LS polyester +50% ATH filler C B B A C D A B E A C E D E

Vacuum Bag Moulding CSM/Polyester E B C A E C A A D A E B D E

Glass/Epoxy Prepreg (hot melt) C C B A B E D B D B A D C A

Carbon/Epoxy Prepreg (hot melt) E E E E C A B E B E A B B A

Co-mingled glass/Polypropylene A B B A B A A B B A A B C A

Continued . . .

32 green guide ratings green guide to composites


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RTM Woven Glass/Polyester C C C A C E A B B A A D C E

Hemp/Polyester B B B A D A A B B A A A C E

Carbon/Polyester D D E E D A A E B D A A C E

Woven Glass/Polyester +50% CaCO3 filler B B B A B E A B A A A E D E

Woven Glass/Polyester +50% ATH filler B C B A B E A C C A A E C E

Resin Infusion Woven Glass/Polyester D B C A D D A B C A B C C C

Hemp/Polyester D B C A E A A A D A C A C C

Woven Glass/Low styrene (LS) polyester C B C A D D A B C A B C C C

Woven Glass/Epoxy B C A A A E D C C B A D C C

Autoclave Moulding Glass/Epoxy Prepreg (hot melt) B C B A A E C B C B A D B A

Carbon/Epoxy Prepreg (hot melt) D D E E B A B E B E A B B A

Compression Moulding SMC C B C A D A A B C A A C B D

PP/PP A B B A A A A C B A A A A D

GMT A B B A A B A C B A A B A D

LFT A B B A A B A C A A A B A D

All the processes modelled in this study can be used to manufacture this component except for pultrusion because this component is not of constant cross-section.

From looking at the base cases where the material is a standard polyester/glass combination it can be seen that the closed mould processes (RTM and resin infusion) perform better environmentally than open mould processes (hand lay-up, vacuum bagging and spray-up).


Flat Sandwich Panel 1m x 8m A generic component measuring 1m x 8m with a 25mm thick core, having a panel bending stiffness equivalent to a sandwich panel with a 4mm thick chopped strand mat skin. For the pultrusion process the component is modelled with ribs instead of the core material used in other processes. This component is designed to be representative of large-scale applications such as bridge decks and marine structures.


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Vacuum Bag Moulding CSM/Polyester E C E A E D A B D A E B C E

RTM Woven Glass/Polyester B C C A B E A B B A A C B E

Resin Infusion Woven Glass/Polyester C B C A C D A B C A B C B C

Autoclave Moulding Glass/Epoxy Prepreg (hot melt) A B A A A D B B C B A C A B

Pultrusion Woven glass and glass rovings/Polyester +CaCO3 filler A A A A B B A A A A C C B A

Hand Lay-Up CSM/Polyester E C E A E D A B D A E C C E

Woven Glass/Polyester C B C A C D A B C A C C B E

Hemp/Polyester E B D A E A A B D B E A C E

CSM/Polyester +50% CaCO3 filler C A B A C D A A B A D E D E

CSM/Polyester +50% ATH filler D B C B C E A C E A D E D E

CSM/Low styrene (LS) polyester E C E A E D A B D A C C C E

CSM/LS polyester +50% CaCO3 filler B A B A C D A A B A C E D E

CSM/LS polyester +50% ATH filler C B C B C E A C E A C E D E

Woven Glass/Epoxy B C A A A E C C C C A C B E

CSM/Epoxy C E B A B E E E E E A D C E

Woven Glass/LS polyester +50% CaCO3 filler A A A A B D A A B A B D C E

Vacuum Bag Moulding CSM/Polyester E C E A E D A B D A E B C E

Glass/Epoxy Prepreg A B A A A D B B C B A C A A

Carbon/Epoxy Prepreg A B B E A A A C B C A A A A

Co-mingled glass/Polypropylene A A B A B A A B B A A B B A

Spray-up Glass rovings/Polyester E C E A E C A C D A D B C E

Glass rovings/Polyester+50% ATH filler D C D B C E A D E B C E D E

Glass rovings/Polyester+50% CaCO3 filler C B C A C C A B B A D D D E

Glass rovings/Low styrene (LS) polyester E C E A E C A C D A C B C E

Glass rovings/LS polyester +50% ATH filler C C D B C E A D E B B E D E

Glass rovings/LS polyester +50% CaCO3 filler C B C A C C A B B A B D D E

Continued . . .

34 green guide ratings green guide to composites


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RTM

Woven Glass/Polyester B C C A B E A B B A A C B E

Hemp/Polyester B B B A C A A B C B A A B E

Carbon/Polyester A B C E B A A C A C A A A E

Woven Glass/Polyester +50% ATH filler A B B A B E A B B A A D B E

Woven Glass/Polyester +50% CaCO3 filler B C B A B E A C B A A E B E

Carbon/Polyester +50% CaCO3 filler A A B E A A A C A C A A A E

Resin Infusion Woven Glass/Polyester C B C A C D A B C A B C B C

Polyester/Hemp D C D A E A A B D B C A C C

Low styrene polyester/Woven Glass C B C A C D A B C A A C B C

Low styrene polyester/Hemp D C D A E A A B D B B A C C

Woven Glass/Epoxy B C A A A E C C C C A D B C

Autoclave Moulding

Glass/Epoxy Prepreg (Hot melt) A B A A A D B B C B A C A B

Carbon/Epoxy Prepreg (Hot melt) A B B E A A A C A C A A A B

Pultrusion Woven glass and glass rovings/Polyester+ CaCO3 filler A A A A A C A A A A B C B A

Woven glass and glass rovings/Polyester+ ATH filler A A A A A D A A B A B D B A

All processes are modelled except compression moulding as the component is too large for this process.

A similar trend can be seen as for the double curvature panel, with the open mould processes performing worse. Because the sandwich panel is thicker than the double-curvature flat panel, lower amounts of higher performance fabrics are needed to give equivalent bending stiffness to a 4mm thick chopped strand mat laminate. These materials therefore show improved impact results compared to those for the double curvature panel.


Complex Moulded ComponentA complex moulded component, modelled as having a fixed volume of 770cm3, where the other components have been modelled as having a fixed panel bending stiffness. This component has been selected as being typical of a part with more features and complexity (eg ribs and bosses) that can typically be manufactured using an open mould process.


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RTM Woven Glass/Polyester B B B A C E A A C A C D D E

Autoclave Moulding Glass/Epoxy Prepreg (hot melt) B B A A A D E B E A A D B B

Compression Moulding SMC B A B A D A A A C A B C C D

RTM Woven Glass/Polyester B B B A C E A A C A C D D E

Hemp/Polyester B A A A C B A A C A C A C E

Carbon/Polyester E D E E E B A E C D C A C E

Woven Glass/Polyester +50% ATH filler B B B A B E A A D A B E D E

Woven Glass/Polyester +50% CaCO3 filler B A A A B D A A A A A E D E

Hemp/Polyester +50% CaCO3 filler A A A A B A A A A A A B C E

Autoclave Moulding Glass/Epoxy Prepreg (hot melt) B B A A A D E B E A A D B B

Glass/Epoxy Prepreg (hot melt) E E E E C A D E D E A B B B

Compression Moulding SMC B A B A D A A A C A B C C D

PP/PP A A A A A A A A A A A A B D

GMT A A A A A A A A A A A A B D

LFT A A A A A B A A A A A B B D

The only processes that can make the complex moulded component are RTM, autoclave moulding and compression moulding.

It should be noted that because this component has been modelled as having a fixed volume, it is not possible to reduce quantities of materials used by using materials with better structural qualities. Thus materials of low environmental impact by volume (hemp and filled polyesters) perform well for this component and materials of high environmental impact, in particular carbon, perform badly for this component.

36

ATH Alumina TrihydrateBRE Building Research EstablishmentCFC ChlorofluorocarbonsCNC Computer Numerically ControlledCSM Chopped Strand MatGMT Glass Mat ThermoplasticHCFC Hydro ChlorofluorocarbonsLCA Life Cycle Assessment LFT Long Fibre ThermoplasticMEKP Methyl Ethyl Ketone PeroxideNGCC Network Group for Composites in ConstructionPP PolypropylenePPE Personal Protective Equipment Prepreg Pre-Impregnated FibrePVA Poly Vinyl AcetatePVC Poly Vinyl ChlorideRTM Resin Transfer MouldingSMC Sheet Moulding CompoundUV Ultraviolet VOCs Volatile Organic Compounds

glossary

green guide to compositesan environmental profiling system for composite materials and products

This guide has been created to allow the composites industry to understand

the environmental and social impacts of different composite materials and

manufacturing processes. The life-cycle impacts of each material and process

choice from the cradle to the factory gate are presented in simple A to E

comparative rankings, for the first time allowing informed decisions to be made on

the environmental and social effects of composite materials and process choices.

Documents

KN1607 green guide v6.indd - NetComposites